The field of the present invention relates, in general, to an apparatus and method for optical imaging, and, in particular, to an apparatus and method for optical imaging that includes distancing and automatic focusing capability.
In the past, at least three conventional approaches were used to obtain a focused image in an imager, 1) using a small aperture (Large F-Stop) adjacent the imaging lens to create a large depth of field 2) using ultrasonic detection with an autofocusing apparatus and 3) using high-powered laser detection with an autofocusing apparatus. Each of these approaches will be described briefly.
In the first approach, a small aperture adjacent the imaging lens allows for a large depth of field such that an object will be in focus provided it falls within the depth of field. A drawback, however, is that the small aperture permits less light to travel through the lens, yielding poorer contrast and image quality. As a result, a separate light source is required for this approach, adding to its complexity and cost. The large depth of field also renders it difficult to accurately determine the distance from the lens to the object. Finally, the small aperture yields a lower optimal resolution for the image.
The second approach employs ultrasonic sound waves to determine the distance to an object from the lens of the imager, and based on this distance, a separate autofocusing apparatus is used to focus the image. Ultrasonic waves directed at the object reflect off the object, back to an ultrasonic detector. Based on the time lapse and/or the phase shift between the emission wave and the detected wave, the distance to the object may be determined. A lens positioning mechanism or other autofocus apparatus adjusts the focus based on the determined distance. A drawback with this technique is that two separate wave paths are used to focus and capture an image, the first path is the ultrasonic path and the second is the image path. Ultimately, the two paths make the system more complex, and in the case where the ultrasonic emission system is not integrated with the image detection system, over time the systems may become miscalibrated, leading to blurred images.
The third approach employs a high-powered laser to determine the distance from the image lens to an object, and based on this distance, a separate autofocusing apparatus is used to focus the image. The laser projects a laser beam onto the surface of an object, creating a laser spot. The projected laser spot is viewed from an angle relative to the laser beam, and the position of the reflected spot image allows the instantaneous distance of the object""s distance to be gauged. A separate autofocus apparatus uses this distance information to manipulate the lens to bring the object into focus. Along with the complexity added by the separate laser emission detection system, another drawback of this approach is that the potential exposure of high-powered laser light to the eyes of workers presents a potential human safety hazard.
Thus, the present inventor has recognized a need for an integrated apparatus capable of automatically focusing an image of an object, yielding high-quality optical resolution, even in low light conditions, without the potential health hazards associated with laser light radiation.
The present invention in one aspect is directed to an automatic focusing and optical imaging apparatus for optical imaging of an object. In a preferred construction, the apparatus includes at least one lens, a distancing sensor adapted to receive light rays representative of the image that travel through the at least one lens, an imaging sensor adapted to receive light rays representative of the image that travel through the at least one lens, and at least one processor coupled to the distancing sensor and the imaging sensor for controlling the movement of the imaging sensor to a position for optimal imaging, and processing the image received by the imaging sensor.
Yet another aspect of the invention includes a method for automatically focusing and optical imaging an object using an automatic focusing and optical imaging apparatus. The method includes determining the distance from the automatic focusing and optical imaging apparatus to the object using a distancing sensor in the apparatus, adjusting the position of an imaging sensor in the apparatus to a position for optimal imaging based on the distance determining step, and optically imaging the object using the imaging sensor.